DS17887 查看數據表（PDF） - Maxim Integrated

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DS17887

Real-Time Clocks

Maxim Integrated 

DS17285/DS17287/

DS17485/DS17487/

DS17885/DS17887

Real-Time Clocks

General Description

The DS17285, DS17485, DS17885, DS17287, DS17487,

and DS17887 real-time clocks (RTCs) are designed to

be successors to the industry-standard DS12885 and

DS12887. The DS17285, DS17485, and DS17885 (here-

after referred to as the DS17x85) provide a real-time

clock/calendar, one time-of-day alarm, three maskable

interrupts with a common interrupt output, a program-

mable square wave, and 114 bytes of battery-backed

NV SRAM. The DS17x85 also incorporates a number

of enhanced functions including a silicon serial number,

power-on/off control circuitry, and 2k, 4k, or 8kbytes of

battery-backed NV SRAM. The DS17287, DS17487, and

DS17887 (hereafter referred to as the DS17x87) integrate

a quartz crystal and lithium energy source into a 24-pin

encapsulated DIP package. The DS17x85 and DS17x87

power-control circuitry allows the system to be powered

on by an external stimulus such as a keyboard or by a

time-and-date (wake-up) alarm. The PWR output pin is

triggered by one or either of these events, and is used to

turn on an external power supply. The PWR pin is under

software control, so that when a task is complete, the

system power can then be shut down.

For all devices, the date at the end of the month is auto-

matically adjusted for months with fewer than 31 days,

including correction for leap years. It also operates in

either 24-hour or 12-hour format with an AM/PM indicator.

A precision temperature-compensated circuit monitors

the status of VCC. If a primary power failure is detected,

the device automatically switches to a backup supply. A

lithium coin cell battery can be connected to the VBAT

input pin on the DS17x85 to maintain time and date oper-

ation when primary power is absent. The DS17x85 and

DS17x87 include a VBAUX input used to power auxiliary

functions such as PWR control. The device is accessed

through a multiplexed byte-wide interface.

Applications

●● Embedded Systems

●● Utility Meters

●● Security Systems

●● Network Hubs, Bridges, and Routers

Features

●● Incorporates Industry-Standard DS12887 PC

Clock Plus Enhanced Functions

●● RTC Counts Seconds, Minutes, Hours, Day, Date,

Month, and Year with Leap Year Compensation

Through 2099

●● Optional +3.0V or +5.0V Operation

●● SMI Recovery Stack

●● 64-Bit Silicon Serial Number

●● Power-Control Circuitry Supports System Power-

On from Date/Time Alarm or Key Closure

●● Crystal Select Bit Allows Operation with 6pF or

12.5pF Crystal

●● 12-Hour or 24-Hour Clock with AM and PM in

12-Hour Mode

●● 114 Bytes of General-Purpose, Battery-Backed NV

SRAM

●● Extended Battery-Backed NV SRAM

• 2048 Bytes (DS17285/DS17287)

• 4096 Bytes (DS17485/DS17487)

• 8192 Bytes (DS17885/DS17887)

●● RAM Clear Function

●● Interrupt Output with Six Independently Maskable

Interrupt Flags

●● Time-of-Day Alarm Once per Second to Once per

Day

●● End of Clock Update Cycle Flag

●● Programmable Square-Wave Output

●● Automatic Power-Fail Detect and Switch Circuitry

●● Available in PDIP, SO, or TSOP Package

(DS17285, DS17485, DS17885)

●● Optional Encapsulated DIP (EDIP) Package with

Integrated Crystal and Battery (DS17287,

DS17487, DS17887)

●● Optional Industrial Temperature Range Available

●● Underwriters Laboratory (UL) Recognized

Ordering Information, Pin Configurations, and Typical

Operating Circuit appear at end of data sheet.

19-5222; Rev 2; 5/16

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